The present invention relates to an image processing apparatus and an image processing method, and for example, is suitably applied to television receivers.
Conventionally, a CRT (Cathode Ray Tube) is adopted in a television receiver as a display device for displaying received images. This CRT is designed to display images by sequentially scanning and brightening points on a fluorescent screen with an electronic beam irradiated from the top left to the bottom right.
An image displayed on a CRT in this manner is comprised of the points on the fluorescent screen, i.e. a set of pixels, which can be regarded as digital signals resulting from the sampling of the original image at the pixel positions of the fluorescent screen. For instance, a displayed image obtained by shooting a natural scene is comprised of digital signals obtained by sampling the actual natural scene comprised of analog signals treating the pixel positions of the fluorescent screen as sampling points.
Incidentally, in a television receiver, unless the so-called principle of sampling, i.e. the principle that, in order to reproduce the original analog signals from digital signals obtained by sampling the analog signals, the sampling should be performed at a frequency at least double the maximum frequency of the analog signals, is satisfied in sampling the original image, the signal level widely fluctuates and the ariasing occurs in an image to be displayed on the CRT.
Generally in a television receiver, since images are displayed on the CRT by sequentially scanning the fluorescent screen with an electronic beam from the top left to the bottom right, the horizontal direction in which the scanning line runs is pre-filtered to satisfy the principle of sampling, and the vertical direction orthogonal to the scanning line is not pre-filtered, resulting in the problem of ariasing occurring in the vertical direction of the displayed image.
For instance, in the case of taking note of a random vertical direction in the N-th frame of a displayed image as illustrated in FIG. 11, if the original image in that vertical direction has a signal component of a frequency higher than xc2xd of the frequency corresponding to a single line (horizontal scanning period) as denoted by solid lines in the figure, the aforementioned principle of sampling is not satisfied, resulting in causing ariasing and preventing the original image from being displayed correctly, but only the image denoted by dotted lines in the figure can be displayed. Such ariasing affects signal processing for Y (luminance signal)/C (color signal) separation, noise removal and picture quality improvement, and various other signal processing which are performed by the television receiver.
Even ariasing occurs, if there is no change in a pixel value at each pixel, only the resolution of the displayed image is deteriorate, but the audience feels no particular awkwardness. However, regarding an image of a scene in which, for instance, a tree covered with many leaves is swaying in the wind, the signal represented by a solid line in the figure in the N-th frame changes to a signal represented by a solid line in the (N+1)-th frame. Change of an image having ariasing in this way makes the audiences feel very awkward.
Incidentally, in the case of taking note of a random single frame of a displayed image, since the displayed image has ariasing in the vertical direction, it is difficult, in view of the principle of sampling, to reproduce the original image having a high frequency component from only that single frame of the displayed image. Also, it is also difficult to reproduce the original image by pre-filtering in the vertical direction an image already having ariasing in the vertical direction.
The present invention, attempted in view of the above-noted problems, is intended to propose an image processing apparatus and an image processing method which can remarkably improve picture quality as compared with the prior art.
In order to solve these problems, according to the present invention, when second image data is generated from first image data, a plurality of images which are different from a current image data of the first image data with respect to a temporal direction is stored in a plurality of memories, a movement between the current image and each of the plurality of images stored in the plurality of memories is detected, an image stored in any one of the plurality of memories is updated to the current image according to each of the detected movements and moreover, any one of the plurality of images stored in the plurality of memories units is selected according to each of the detected movements to correct the positions of the selected image according to the movement of the image, and the image corrected by a correcting section and the current image are combined to generate the second image data having the larger number of pixels than the first image data.
A movement vector between each of image data stored in a plurality of memories and the current data is detected, and image data in the storage unit is updated and image data to be combined is selected based on the detection results, thereby processing of correcting the position of any of the image data stored in the plurality of memories and combining the resultant with the current image data can be performed with a further improved accuracy.